JPH0589788A - Dielectric support for travelling wave tube - Google Patents

Abstract

PURPOSE:To suppress the electrostatic charge amount of a dielectric support and prevent the disorder of electron beam passing a high frequency circuit by forming an alumina coating layer on the surface of the dielectric support to support the high frequency circuit. CONSTITUTION:The surface of a dielectric support for a travelling wave tube is coated with a dielectric material having 1 or higher secondary electron emitting ratio in the case primary electron with eE (eV) energy comes in wherein E (V) stands for the potential of a high frequency circuit part and (e) (Coul) for the battery's charge. That is, a dielectric support 1 of boron nitride(BN) is coated with a thin alumina 2 coating and a part of the electrons emitted from the cathode, having 10 kev kinetic energy, are sent in the support 1 from the high frequency circuit in the case that the voltage E (V) between the cathode of a travelling wave tube and the high frequency circuit is 10 keV. In that case, the electrostatic charge amount of the support 1 is suppressed and the electron beam passing the high frequency circuit is prevented from being disordered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric support for a traveling wave tube, and more particularly to an antistatic structure for the dielectric support.

[0002]

2. Description of the Related Art A traveling wave tube has a high-frequency circuit that interacts a high frequency with an electron beam to amplify the high frequency. In a helix or phosphorus group type traveling wave tube,
The high frequency circuit is usually supported in a vacuum sealing metal pipe by three dielectric columns.

FIG. 3 shows the structure of a high frequency circuit section of a helix type traveling wave tube. The high frequency circuit 3 is supported by a dielectric support 5 in a vacuum sealing metal pipe 4. Usually, three dielectric support columns 5 are arranged at 120 ° intervals and support the high frequency circuit 3 in the metal pipe 4. An example of a conventional dielectric strut is shown in FIG. Conventionally, alumina (Al ₂ O ₃ ) or beryllia (BeO) has been used as a dielectric strut material, but recently, boron nitride (BN) having a small dielectric constant is used to improve the efficiency of the traveling wave tube. It is starting. However, boron nitride may be charged by the electron beam passing through the high-frequency circuit during the traveling-wave tube operation to cause a potential change, which may cause instability of the electron beam trajectory and damage the high-frequency circuit.

Conventionally, in order to prevent the electrification of boron nitride, there is also an example in which carbon is thinly coated on the surface of boron nitride so that electric charges flow through a coating layer to a high frequency circuit or a metal pipe for vacuum sealing. is there.

[0005]

However, the carbon coating of the prior art leads to an increase in high frequency loss,
There is a drawback in that the output and gain of the traveling wave tube are reduced.

[0006]

In the dielectric support for a traveling-wave tube according to the present invention, the electric potential of the high-frequency circuit portion with respect to the cathode potential of the traveling-wave tube is E (V), and the battery charge is e (Coul). , EE (eV) primary electrons are incident, the surface is coated with a dielectric material having a secondary electron emission ratio equal to or more than 1. Alumina and beryllia are suitable as the dielectric to be coated.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing a first embodiment of the present invention.
Alumina 2 is thinly coated on a boron nitride dielectric pillar 1. FIG. 2 shows the secondary electron emission ratio of boron nitride and alumina.

Now, assuming that the voltage E (v) between the cathode and the high frequency circuit of the traveling wave tube is 10 kv, the electrons emitted from the cathode have a kinetic energy of 10 kev and pass through the high frequency circuit, and a part of it is dielectric. It is incident on the body pillar. When the dielectric strut is composed of only boron nitride, as can be seen from FIG. 2, the secondary strut emission ratio of the dielectric strut is 1 or less, so that the dielectric strut accumulates electrons and becomes negatively charged to the periphery. Lower the potential of. As a result, the trajectory of the electron beam passing through the high frequency circuit becomes unstable.

On the other hand, in the case where the dielectric pillar has a structure in which boron nitride is coated with alumina as shown in FIG. 1, the secondary electron emission ratio of alumina is larger than 1 even when the electron is incident at 10 kev as shown in FIG. As such, the dielectric struts do not become negatively charged. In addition, the dielectric support may be positively charged, but if it is positively charged, the potential of the dielectric support will be raised and secondary electrons will be returned to the dielectric support, so the amount of positive charge is small and high frequency It does not disturb the trajectory of the electron beam passing through the circuit.

As described above, in the dielectric pillar in which the boron nitride is coated with alumina, the charge is suppressed even by the collision of the electron beam and the peripheral potential is not changed so much that the disturbance of the electron beam is not caused. . Further, since alumina is a dielectric substance, it does not have a Joule loss unlike carbon coating, and does not cause a gain reduction or output reduction of a traveling wave tube.

As a second embodiment of the present invention, it is possible to cite an example in which a dielectric pillar of boron nitride is coated with beryllia instead of alumina. When used in the same traveling wave tube as in the first embodiment, the first
In the same manner as in the first embodiment, antistatic property and electron beam orbital disturbance prevention can be expected, and beryllia has a higher thermal conductivity and a lower dielectric constant than alumina. It is expected that the heat dissipation effect and efficiency will be increased.

The alumina or beryllia dielectric coating can be performed by CVD or ion plating.

[0013]

As described above, in the dielectric support for a traveling wave tube of the present invention, the primary electron of eE (ev) is incident with the voltage between the cathode and the high frequency circuit of the traveling wave tube being E (v). In this case, the secondary electron emission ratio is equal to or more than 1, and the surface is coated with a dielectric, so that the charge of the dielectric support is suppressed and the electron beam passing through the high frequency circuit is not disturbed. Have.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a dielectric pillar according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a secondary electron emission ratio of a dielectric.

FIG. 3 is a cross-sectional view showing the structure of a high frequency circuit section of a traveling wave tube.

FIG. 4 is a cross-sectional view showing a conventional dielectric strut.

[Explanation of symbols]

 1 BN support 2 Alumina coating layer 3 High frequency circuit 4 Metal pipe 5,6 Dielectric support

Claims (3)

[Claims] 1. A dielectric strut for supporting a high-frequency circuit of a traveling-wave tube, wherein the voltage between the cathode and the high-frequency circuit of the traveling-wave tube is E (V), and the electronic charge is e (Coul), eE
A dielectric column for a traveling-wave tube, characterized in that the surface thereof is coated with a dielectric having a secondary electron emission ratio equal to or more than 1 when primary electrons of (eV) are incident. 2. The dielectric pillar for a traveling wave tube according to claim 1, wherein the dielectric to be coated is alumina. 3. A dielectric support for a traveling wave tube according to claim 1, wherein the dielectric to be coated is beryllia.